The present invention relates to a modular support element adapted to form a support for a corresponding staircase tread and to be connected to contiguous elements to form a staircase.
Staircases are known which comprise a plurality of modular support elements each of which has a plurality of walls of rather complicated shape for forming a support platform for the respective tread and suitable coupling seats for the connection of that element to contiguous ones; such staircases also include a plurality of spacer members, normally of plate shape, each of which is adapted to be inserted between two contiguous modular elements, as well as a plurality of threaded connecting members which are arranged to interconnect the contiguous modular elements with the spacer members interposed between them.
The threaded connecting members include at least one bolt which is adapted to pass through an elongate aperture formed in one wall of each modular element and a hole formed in another wall of the contiguous element; this bolt, which is normally locked by a nut, serves to connect two contiguous elements together.
Modular support elements of the type described and staircases made therefrom have several disadvantages.
First of all, they do not enable the height of the step riser to be adjusted simply and quickly; indeed this height is adjusted by the interposition of a spacer member between two contiguous elements: the operations which are needed for the interposition of this member and for locking together the two elements between which the member has been inserted require particular care and skill. Moreover, in order to satisfy the need for staircases to be constructed with different riser heights, it is necessary to provide a large number of spacer members of different dimensions. Furthermore the tread depths of the various steps may be achieved only to a certain approximation since this depth is determined simply by the sliding of one modular element longitudinally relative to the contiguous element, which movement is allowed by the presence of the aforesaid aperture in one of the walls of each element.
The resistance which each modular element presents to rotation relative to the contiguous element about a vertical axis is thus rather poor; indeed, this resistance depends solely on the frictional torque generated between these elements and this depends on the degree to which the bolt which connects the elements is tightened during assembly and hence the degree to which the bolt is stressed and obviously this cannot reach very high values. As a result, therefore, small rotational movements can occur between one element and the contiguous one even when the staircase has been assembled.
Finally, in order to form staircases whose modular elements are arranged in a predetermined angular configuration relative to each other, long and complicated assembly operations are needed; indeed, in order to place two contiguous elements in a predetermined angular configuration it is necessary to measure the respective angle or to use suitable checking equipment.